Solomon led efforts to identify the cause of the ozone hole over Antarctica.

An American atmospheric chemist who led efforts to identify the cause of the Antarctic ozone hole and a French geochemist who extracted the longest-yet climate record from polar ice cores have won the prestigious 2012 Vetlesen Prize. Susan Solomon and Jean Jouzel will share the $250,000 award, considered to be the earth sciences’ equivalent of a Nobel.

“Earth Science is a collective enterprise, and transformational advances are the product of many authors,” says the Vetlesen Prize committee’s citation. “Both nominees have made leading and fundamental contributions to climate science.” The prize is funded by the G. Unger Vetlesen Foundation in New York and administered by Columbia University’s Lamont-Doherty Earth Observatory.

Solomon’s work in identifying the cause of Antarctica’s springtime ozone losses helped bring about a global ban on manmade ozone-depleting chemicals. Working most of her career at the National Oceanic and Atmospheric Administration (NOAA) in Boulder, Colo., Solomon proposed in a 1986 study that refrigerants and other industrial chemicals were responsible for the Antarctic ozone hole discovered a year earlier. She led two expeditions to Antarctica, in 1986 and 1987, bringing back key measurements that proved her hypothesis. Recognizing that ozone protects the planet from harmful ultraviolet rays that can cause skin cancer, policymakers around the world responded with rare speed: in 1987, they agreed on a Montreal Protocol to phase out the use of chlorofluorocarbons (CFCs) and related chemicals.

Solomon and her colleagues also explained why ozone destruction was greatest during southern spring. Throughout the dark and extremely cold winter, CFC byproducts react with icy stratospheric clouds to produce ozone-depleting chlorine compounds. When sunlight returns to the South Pole, it reacts with the compounds to break ozone apart. In a 2002 study, Solomon and a colleague also linked Antarctica’s ozone hole to a strengthening of winds that circle the continent in summer, causing net cooling over most of Antarctica but extreme warming over the West Antarctic Peninsula. She has also written several books. In The Coldest March, published in 2002, she reconstructed the weather during British explorer Robert Scott’s 1911 expedition to Antarctica to argue that abnormally cold conditions and not incompetence led to the deaths of Scott and his crew. She has also worked as a member of the Intergovernmental Panel on Climate Change (IPCC),which in 2007 received the Nobel Peace Prize. Solomon, 56, is the first woman to win the Vetlesen since it was first offered in 1960.

Jouzel has assembled the longest climate record yet from polar ice cores

Jouzel, 65, has been involved in collecting ice-core records from both poles since the 1970s, and has advanced isotopic techniques for extracting past climate information from them. In the longest climate reconstruction yet from ice cores, Jouzel in a 2007 study in the journal Science charted temperatures in Antarctica for the last 800,000 years, over eight consecutive ice ages. The record was long enough to highlight Antarctica’s climate response to slowly varying seasonal distribution of sunlight caused by changes in earth’s orbit. It was also detailed enough to reveal climate variations within each ice age cycle due to earth’s complex internal climate system.

He has also been a leader in bringing human-caused climate change to the public’s attention.

For the last 20 years, he has worked on the IPCC, and is currently vice president of the climate science working panel, whose findings will be released in the Fifth Assessment Report next September. Jouzel has co-written several books, including Climate: A Dangerous Game in 2007 and White Planet, whose English translation is due out in 2013.

Neither scientist came from a scientific family. Solomon was born and raised in Chicago; her father sold insurance and her mother taught fourth grade. She says she was inspired to become a scientist by watching oceanographer Jacques Cousteau on TV as a child, and to go into chemistry by the “exactness” of the experiments she did in high school. “You have a clear solution and you add an exact amount of base and wow, it changes to a bright color just like it’s supposed to,” she said. She received her Ph.D. from the University of California at Berkeley in 1981, and worked at NOAA until 2011, when she became a professor at the Massachusetts Institute of Technology. She has won many previous honors: the American Geophysical Union (AGU)’s Macelewane Medal in 1985 for early-career achievement; a U.S. National Medal of Science in 1999, and the Blue Planet Prize in 2004.

Jouzel grew up in a farming family in Brittany, and during his graduate studies in chemistry became interested in how large hailstones form in the atmosphere at a time when chemical seeding of clouds to produce rain was a popular research topic. He received his Ph.D. in chemistry from the Faculté d’Orsay in Paris in 1974 and eventually applied his hail-investigation techniques to polar ice cores, advancing methods for pulling climate information from air bubbles trapped in the ice and minute variations in water molecules layered in the cores.

He has spent his research career at the French nuclear agency, CEA, or Commissariat à l'Energie Atomique. In 1995, he became research director of CEA’s climate and environment lab (LSCE), and from 2001 to 2008, headed the Institut Pierre-Simon Laplace, a national climate research lab near Paris that includes LSCE. In 2002, Jouzel and his mentor Claude Lorius received France’s highest scientific honor, the CNRS gold medal, for their work on polar ice cores, including reconstruction of past greenhouse gas levels from air trapped in the ice. In 1997, he was awarded the European Geophysical Society’s Milankovitch Medal for outstanding research on long-term climate change and modeling; and in 2003, AGU’s Roger Revelle medal for outstanding contributions to atmospheric science.

Solomon (left) has traveled to Antarctica several times to gather measurements in the field. (Alexandra Weaver)

“If we want to avoid large climate change we need to act now on greenhouse gases,” he said. “Global warming is not yet damaging, but if we do nothing in the coming years we will have more extreme events, droughts, storms and so on.”

The Vetlesen Prize is given “for scientific achievement resulting in a clearer understanding of the Earth, its history, or its relations to the universe.” It was established in 1959 by the trustees of the estate of G. Unger Vetlesen, a Norwegian immigrant to the United States who became a leading shipbuilder, World War II military leader and pioneer in transatlantic air travel. Vetlesen passed away in 1955. Designed to recognize sweeping achievements on par with the Nobel, it is given every several years by a selection committee appointed by the president of Columbia University. The most recent award was in 2008 to maverick geologist Walter Alvarez, who convinced the world that an asteroid strike wiped out the dinosaurs. Previous winners include British climate scientist Sir Nicholas Shackleton, and several scientists at Lamont-Doherty itself, including climate scientist Wallace Broecker, marine geologist Walter Pitman, seismologist Lynn Sykes and Lamont’s founding director Maurice “Doc” Ewing.

Solomon and Jouzel will receive the award and accompanying medal at the university’s Low Library on Feb. 21.